From Destruction to Reconstruction: Substrate-Driven Biosynthesis of Antioxidants from Antibiotic Residues in Hyperthermophilic Composting

The accumulation of tetracycline (TC) in organic fertilizer poses severe risks by fostering antibiotic resistance in soil ecosystems. Hyperthermophilic composting effectively mitigates these threats, achieving near-complete TC removal via thermal selection. Although previous studies have widely characterized the catabolic degradation routes of TC, we propose a novel transformation pathway where TC-derived intermediates are redirected into secondary metabolism to synthesize antioxidant alkaloids and flavonoids. Integrated abiotic-biotic controls first demonstrated that while heat initiates breakdown, hyperthermophilic microbiota drive the subsequent deep transformation and diversification of products. FT-ICR-MS revealed this process is underpinned by substrate restructuring, where recalcitrant compounds are depolymerized into thermodynamically favorable low-molecular-weight organic matter (LMW-OM). Cross-feeding assays confirmed this accessible substrate pool significantly enhances co-metabolic efficiency compared to conventional composting-derived substrates. Mechanistically, multi-omics indicated LMW-OM elevates intracellular NADH and ATP within the Thermus-dominated community, shifting metabolism from maintenance to active biosynthesis. Consequently, TC intermediates acting as structural mimics of endogenous aromatic precursors are recruited into these energized pathways to generate antioxidants. Crucially, diverting residues into anabolic networks eliminates the selective pressure exerted by intermediates, explaining the extensive attenuation of antibiotic resistance genes. This work highlights pivotal substrate-microbe interplay, offering a new paradigm for converting antibiotic-laden waste into functional bio-organic fertilizers.